PDCD1 and cancer: The most prominent immune checkpoint blocking strategies, such as targeting cytotoxic T lymphocyte‐associated protein 4 (CTLA‐4) and blocking the interaction between programmed cell death 1 (PD‐1) and PD ligand 1 (PD‐L1), are able to enlist and strengthen the immune system to attack cancer cells and have achieved clinical success in several cancer types, even in metastatic and chemoresistant cancer.13, 14